A Tree that shakes off its Leaves
I've found a solution that's pretty simple with the help of this video: https://www.youtube.com/watch?v=lPCs4XbGth8

Basically, create a controller particle system that manages other particles systems. Then create the first (1) particle system which keeps the leaves tracked onto the tree, using No 'Physics'. Then, create a second (2) particle system in the same position, which uses Newtonian physics and Brownian motion.

In the controller cube, the first key should be attached to (1) and second key should be attached to (2) and you can use timing to set how long you want the leaves to stay attached.



It's an alright start: https://imgur.com/a/I6dVId5

One problem is, the leaves fall off all at once. The Brownian motion can hide this and make it look like some leaves stay attached for a bit longer.